In the proposed research we will validate the performance of the OTEG devise on human blood samples. Discarded and de-identified excess human blood samples will be obtained from the MGH coagulation laboratory and from Biological Specialty Corp. (PA, USA). All specimens will be de-identified. Prior to the start of this study, an exempt human subjects protocol will be submitted for approval by the Partners IRB. Research that meets the criteria for Exemption 4 is not considered clinical research as defined by NIH. Therefore, the NIH policies for inclusion of women, minorities and children in clinical research, and targeted/planned enrollment tables, do not apply to research projects covered by Exemption 4.